The M56 Smart Gun is an advanced weapon used by the colonial marines in the movie Aliens. Using electrical pulse action, it fires 60 10mm caseless high-explosive rounds at a rate of 1200 rpm. Despite the fact that the weapon weighs nearly 40 pounds, it can be easily carried and operated with the assistance of a servo-controlled harness. It is called a "smart gun" because the gun has its own guidance system, guided by infrared tracking systems on top of the gun's barrel and on a head-mounted goggle system, guided by a targeting processor in the harness. When a target is designated by the tracking system, the harness automatically guides the operator and gun to the target. Switching targets is as simple as pointing the gun's barrel at a new target. The gun can fire in a three round burst or in fully automatic.

The Smart Gun is a modified MG42 Machine Gun married to a Steadicam harness, with additional parts added from various motorcycles.